Diesel fuel



Patented Sept. 14, 1943 DIESEL FUEL Francis M. Seger, Pitman, and Edwin M. Nygaard, Woodbury, N. .L, assignors to Socony-Vacuum Oil Company, Incorporated, New York, N. Y., a corporation of New York No Drawing. Application April 25, 1941, Serial No. 390,344

6 Claims. (c1. 44 57) This invention has to do in a general way with fuels for internal combustion engines of the compression ignition or Diesel type and is more particularly concerned with the improvement of such fuels by the addition of characterizing ingredients for the purpose of modifying or controlling the combustion characteristics.

In the operation of Diesel engines, where the fuel is injected into a combustion space, it is important to the attainment of maximum emciency that the delay period between injection and ignition be short. Improperly delayed ignition in a Diesel engine gives rise to the phenomenon known as knocking, which is due to improper coordination of combustion and cylinder conditions. By accelerating the ignition of Diesel fuel, it is possible to lower the compression pressure. This insures spontaneous ignition without combustion shock, thereby increasing the ease of starting and the smoothness with which combustion takes place. Also, the low compression pressure permits less weight in the engine and a lower cost per given power output. It is obvious, therefore, that enhanced speed of ignition is a characteristic which is highly desirable in a Diesel fuel.

It has been found that the ignition quality of the fuel oils normally classified as Diesel fuels can be improved by the addition of small amounts of certain compounds which will act as ignition accelerators, thereby decreasing the ignition delay period. This offers a means for improving the better grades of Diesel fuels and a means for widening the range of available fuels by raising the ignition quality of the lower grades to a point where they can be satisfactorily used.

. This invention is based upon the discovery that Diesel fuels of improved ignition quality can be obtained by admixing with the fuel a minor proportion of the oil soluble product (or fraction thereof) obtained by the reaction of rchloromethylmercgptan (C13C.SC1) with elemen ary sulf Perchloromethylmercaptan, as indicated by the formula above, is a chlorinated substituted sulfur chloride and can be prepared by the chlorination of carbon disulfide according to the method of Helfrich and Reid (Joum. Amer. Chem. Soc. 43, 591 (1921)). For example carbon disulflde containing about .4% by weight of iodine was chlorinated in the absence of direct sunlight at a temperature maintained below 25 C. until the volume of the reaction mixture had doubled. The crude product,'which has been topped to remove carbon tetrachloride and sulfur dichloride contains perchloromethylmarcaptan, with some sulfur monochloride. This crude product can be used in the preparation of the reaction products contemplated herein, although in the example cited a fractionated product was used.

Perchloromethylmercaptan may be reacted with elementary sulfur in proportions of about 2.0 parts to about 6.0 parts of the former to one part of the latter. The reaction is best carried out at elevated temperatures of from about 145 to about 170 C. with the heated reaction mixture under a reflux condenser.

The product may be fractionated and purified as hereinafter described or, if desired, after initial topping, it may be treated (as by water washing) to destroy traces of sulfur chloride, and further treated as by dilution with petroleum ether to precipitate elementary sulfur, and then blended with the fuel oil in the desired proportions. Further details in procedures for preparing reaction products which have been found to be especially effective as improvin agents for Diesel fuels, may be obtained from the following examples, which also include data showing the effectiveness of the reaction products contemplated herein, in improving the cetane number of typical Diesel fuels.

Example I To 187 grams (3.9 parts) of perchloromethylmercaptan boiling at -81 C. at mm. pressure was added 48 grams (one part) of elementary sulfur. The mixture was heated in a flask under a reflux condenser at a temperature varying between and 168 C. Total time of heating 11 hours. The product was cut into three fractions by vacuum distillation.

Fraction B. P., o. Yield Grams 90 down to 7... 88 7 down to 1... 71 illed residue" 58 The above fractions including the undistilled residue were distilled again by adding to the bottoms of each cut the next higher bailing out.

Fraction B. P., C. Pressure, mm. Hg Yield Grams (80-155 Atmospheric 64 U5 Atmospheric down to 1 mm. 79 -190 1 mm. up to 2 mm 47 The volatile fraction 1, composed of S2Clz and unreacted CSC14, was discarded. Faction 2 was stirred for two hours with cold water to hydrolyze any SaClz present and then dissolved in petroleum ether and filtered. The product was then purified by double vacuum distillation. Purified product designated at A.

Fraction 3 was freed from elementary sulfur by dilution with petroleum ether which precipitated elementary sulfur. The product was then purified by double vacuum distillation. Purified product designtaed as B.

[Caguaged 3 233 Product 5 S iff? Yield 93s 9501 %s %Cl Grams A 40-130 o.5mo.3 51 29.9 63.9 28.8 63.9

seas of a: Product 6 7- 33%;- Yield %s %c1 3 Grams B "100-175 0.5mo.25.. 34 35.6 60.3 35.1 58.4

The above identified compounds were added to fuels X and Y and the improvement in the ignition quality of the blends ascertained by determination of their cetane numbers. The cetane numbers were determined by the proposed method of the A. S. T. M. (A. S. T. M. Proc. 38 I 392 (1938)).

Fuel X is a straight run number 2 fuel oil possessing the following characteristics.

Gravity, A. P. I 39.8 Flash point (Pensky-Martens F.) 1'72 Aniline point, F 160.5 A. S. T. M. distillation:

Initial F 386 435 90% 572 End point 614 Diesel index 63.9 Cetane number 55 Per cent Cetane Increase Substance blended with fuel X by wt. number of in cetane added blend number 1 58333iiijjiijiiijijiijjiji: 1:3 tit? 13:?

Fuel Y is a catalytically cracked number 2 fuel oil possessing the following characteristics.

Gravity, A. P. I 25.2 Flash point (Pensky-Martens F.) 204 As amodification of the procedure followed in Example I a similar product was prepared by refluxing 3.1 parts of Cl3C.SCl and one part of .sulfur for 50 minutes at a temperature between 151 and 172 C. The mixture was then vacuum distilled, rejecting 54 g. of volatile material distilling at 60 to C. (pot temperature) and 25 mm. pressure, and another 50 g. distilling below C. at 2.5 mm. pressure.

The undistilled residue totaling g. was cornbined with two other batches prepared in a similar manner and the whole added to 500 cc. of methanol and refluxed for one hour at a pot temperature of 70 C. The mixture was allowed to cool and the upper methanol layer rejected. Petroleum ether was added to the lower layer to clarify it and to assist filtration. The filtrate was then topped to remov petroleum ether, the residue constituting the finished product. Analysis of this material showed a sulfur content of 37.7%, chlorine 51.9%. Calculated for (CI3C)2S4 sulfur=35.1%, chlorine:58.4%. This product treated with methanol in the manner just described is improved as to odor over the product obtained by the procedure of Example I.

The reaction product obtained by the foregoing procedure was added to fuel Z, a catalytically cracked number two fuel oil, and the improvement in ignition quality of the blends ascertained by determination of their cetane numbers.

Fuel Z possesses the following characteristics:

It will be observed from the foregoing results the non-volatile reaction products of perchloromethylmercaptan and elementary sulfur as typifled in products of Examples I and II are effective to improve the ignition quality of typical Diesel fuels. It will be observed from the analyses given in Examples I and II that the reaction products contemplated herein contain both sulfur and chlorine in substantial quantities, the sulfur content ranging from about 29 per cent to about 38 per cent and the chlorine content from about 51 per cent to about 64 per cent. The exact chemical composition of the product is uncertain, but the analysis indicates that it is more probably predominantly comprised of (CI3C)2S3 or (01:0)284 or a mixture of these compounds. Because of the uncertainty of the composition, however, the product is described and claimed herein as a reaction product rather than by attempted chemical nomenclature or formula.

The term Diesel fuel, as used herein has reference to those non-viscous petroleum fractions, commonly denoted in the art as Diesel fuels, and to those hydrocarbon oils in general whose physical characteristics render them suitable for use as fuels in compression ignition engines.

The reaction product or products contemplated herein may be used in amounts ranging from about 0.1 percent to about 5.0 percent, and it is to be understood that while we have herein described one preferred procedure for preparing same, the invention is not confined to products made by such procedure, but includes within its scope whatever change or departures fairly come within the spirit of the appended claims.

We claim:

1. An improved Diesel fuel comprising a hydrocarbon fuel oil and in admixture therewith a minor proportion of the non-volatile oil soluble product obtained by reacting perchloromethylmercaptan with elementary sulfur, said non-volatile reaction product containing only carbon in chemical combination with substantial proportions of chlorine and sulfur.

2. An improved Diesel fuel comprising a nonviscous petroleum oil and in admixture therewith a minor proportion of the non-volatile cil soluble product obtained by reacting perchloromethylmercaptan with elementary sulfur, said nonvolatile reaction product containing only carbon in chemical combination with substantial proportions of chlorine and sulfur, and being present in an amount sufiicient to decrease the igni- 4. An improved Diesel fuel comprising a hydrocarbon fuel oil and in admixture therewith a minor proportion of the oil soluble product, from about 0.1 percent to about 5.0 percent, obtained by reacting perchloromethylmercaptan with elementary sulfur, said reaction product containing only carbon in chemical combination with substantial proportions of chlorine and sulfur.

5. An improved Diesel fuel comprising a nonviscous petroleum oil and in admixtur therewith a minor proportion, from about 0.1 percent to about 5.0 percent, of the oil. soluble product obtained by reacting perchloromethylmercaptan with elementary sulfur, said reaction product containing only carbon in chemical combination with from about 51 percent to about 64 percent chlorine and with from about 29 percent to about 38 percent sulfur, and being present in an amount suificient to decrease the ignition delay period of the fuel.

6. An improved Diesel fuel comprising a hydrocarbon oil and in admixture therewith a minor proportion, from about 0.1 percent to about 5.0 percent, of the product obtained by refluxing from two to six parts of perchloromethylmercaptan with 1 part of elementary sulfur at a temperature of from 145 C. to 170 C., and then removing sulfur chloride and uncombined sulfur from the reaction product, the said reaction product containing only carbon in chemical combination with substantial proportions of chlorine and sulfur.

FRANCIS M. SEGER. EDWIN M. NYGAARD. 

